Ex: Communication Networks • Time order the following networks: – Internet (data), radio (audio), television, telephone • Which became established first for mass-use: when & why? Ubiquitous computing: smart devices, environments and interaction 9

PSTN • PSTNs were designed to be very resilient. • Circuit switching can enable a higher Qo. S per call but at the expense of non-optimal use of the channel, – • Interleaved multiple data streams throughput – E. g. , • Later digital telecoms networks Ubiquitous computing: smart devices, environments and interaction 24

Intelligent Networks (IN) • Earliest digital telecommunication networks designed to support specific services, supported using specialised logic contained in specialised switching network elements. • New features / services have to be added and implemented directly in core switch systems -> very long development times for new services • -> Intelligent Networks (IN) network service model, Ubiquitous computing: smart devices, environments and interaction 25

Intelligent Networks (IN) • Supports independent component-based services in general purpose computer nodes rather in special switching nodes. • Enables service providers to drive new services rather than network providers – able to use these to form flexible overlay networks – such as toll free calls, e. g. , “ 0800” numbers. Ubiquitous computing: smart devices, environments and interaction 26

IP Multimedia Subsystems (IMS) • Active development in new IN services has declined in recent years • Focus on development of telecom services & APIs rather than on developing new telecom network protocols. • Although, there seems to be a clear move to IP based networks, in shorter term, hybrid IN and Internet service architectures for mobile users are being proposed such as IP Multimedia Subsystems (IMS). Ubiquitous computing: smart devices, environments and interaction 27

DAB • For digital radio, the Eureka 147 Digital Audio Broadcast (DAB) standard is most commonly used and is coordinated by the World DMB Forum. • DAB uses the MPEG-1 Audio Layer 2 audio (MP 2) codec for audio broadcasting while personal players use the MP 3 codec. • Original objectives of DAB were to ? • DAB+ standard with a better and more efficient transmission codec has been proposed. Ubiquitous computing: smart devices, environments and interaction 37

Network Protocols • Types of packet to data packets called control packets, • • Each data packet is labelled with the address • Enables packets from multiple messages to be multiplexed to use the same part of the network. Ubiquitous computing: smart devices, environments and interaction 41

Routing and Internetworking • Multiple paths may be available • • Data may be too large to be transmitted • Normally performed at the network level without applications being aware of this. Ubiquitous computing: smart devices, environments and interaction 45

Bluetooth • Bluetooth standard for short-range wireless communication over about 1 -100 M • Bluetooth applications include both local communication and increasingly local control. • Unlike IR, Bluetooth does not require a line of sight between the transmitter and receiver. • Current Bluetooth devices and applications include: ? Ubiquitous computing: smart devices, environments and interaction 59

Audio and Video (AV) broadcast Content Based Networks (CBN) • AV CBN oriented to for a regional rather than global customer base. • Video content is richer and it is more likely to be tailored to a specific region in terms of language and culture. • Receivers have limited control over live broadcasts • Video synchronisation with audio (& metadata) is complex Ubiquitous computing: smart devices, environments and interaction 71

Internet and Common Codecs • Internet focussed most on alphanumeric data transmission • support for managing reliable and unreliable data streams, mainly for paired senders and receiver. • support for scalable AV content streamed broadcasts over Internet still maturing • Adoption of compatible standards for the triple-play (audio, video and alphanumeric data) will facilitate their integration. Ubiquitous computing: smart devices, environments and interaction 72

PSDN: IP and UDP • UDP ( User Datagram Protocol) used to support mutlicast –. • Unreliable transport protocols, e. g. , UDP can be used to transmit media streams. • Depending on the protocol and the extent of the loss, receivers may be able to recover the data using Ubiquitous computing: smart devices, environments and interaction 73

Streaming Media over IP networks • Protocols designed to stream media over IP networks. • RTP and RTCP built on top of unreliable UDP • RTSP built on top of reliable TCP Ubiquitous computing: smart devices, environments and interaction 74

Integrating Analogue Video and Text: Teletext • Analogue television broadcast signal can be augmented with text data by embedding this data in the Vertical Blanking Interval or VBI part of the television signal. • In EU: called Teletext data transmission; closed-captioning in USA • …. Ubiquitous computing: smart devices, environments and interaction 79

Power Line Communication (PLC) • An alternative to ubiquitously access data and A-V content. • Wherever there is an electricity PL connection, same network that conducts electricity to deliver energy • PL can be used modulate electricity as a signal and can be used as a channel to communicate data/AV content. • PLC describes a range of systems for using electricity distribution wires for simultaneous distribution of data. Ubiquitous computing: smart devices, environments and interaction 88

Wireless Personal Area Networks (WPAN) • Specified by the IEEE P 802. 15 working group • PAN is normally confined to a person or object typically <10 M in all directions and envelops two or more objects or persons whether stationary or in motion. • Could WLAN standard be used for PANs? – • Bluetooth, Zigbee and IR can be used to implement a PAN. Ubiquitous computing: smart devices, environments and interaction 89

Body Area Network or BAN • Consists of a set of mobile and compact intercommunicating sensors that are either wearable or implanted into the human body. • A typical BAN application can monitor vital body parameters and movements – E. g. , monitor EEG, ECG, and EMG signals • Data Management? – Either to store them in some device on the body for later upload analysis – To periodically transmit data in real-time via some external network interface Ubiquitous computing: smart devices, environments and interaction 91

BAN • Can Bluetooth or Zig. Bee be used for BAN? Ubiquitous computing: smart devices, environments and interaction 92

BAN • Electronic devices can be connected as part of near field BANs to exchange digital information by capacitively coupling picoamp currents through the body (Zimmerman). • Low-frequency carrier, less than one megahertz, was used. Why? – • Zimmerman demonstrated a near-field BAN system to support business processes Ubiquitous computing: smart devices, environments and interaction 93

Mobile User Networks: Design Issues • Design issues include? • We can also classify mobile network support in terms of ? – • Advantage of mobile user support at the network level of the network protocol stack means that mobility, at least to some extent, is transparent to applications. Ubiquitous computing: smart devices, environments and interaction 96

Mobile Addresses • Network location or address for a mobile user needs to be determined in order for a user to receive data. • It is easier to send (somewhere) as the user just has to locate the nearest access network base station. • There are two basic approaches to mobile user addressing: – ? ? . Ubiquitous computing: smart devices, environments and interaction 98

Multi-Path Routing in Mobile Ad hoc Networks (MANETs) • In contrast to fixed computer networks, ad hoc networks: – use connections established for duration of 1 session – require no base station or fixed router. • Ad hoc networks that support mobile nodes are called Mobile Ad hoc Networks (MANETs) • Rather than used dedicated router nodes, each node is willing to forward data for other nodes, and so the determination of which nodes forward data is made dynamically based on the network connectivity, hence the name ad hoc Ubiquitous computing: smart devices, environments and interaction 102

MANETs • Instead, devices discover others within range to form a network for those computers. • Devices may search for target nodes that are out of range by flooding the network with broadcasts that are forwarded by each node. • Connections can be made over multiple nodes (multi-hop ad hoc network). • Routing protocols then provide stable connections even if nodes are moving around. Ubiquitous computing: smart devices, environments and interaction 103

Controlling Network Access: Firewalls, NATs and VPNs • Many ICT resources connected to the Internet are protected to control access to specific resources by specific users or to a closed user group. • If access is not restricted what happens? Ubiquitous computing: smart devices, environments and interaction 112

Controlling Network Access: VPN • Useful to restrict the use of resources on remote networks to specific users that are accessed over a public Internet. • Common technique to achieve this is a VPN • . Ubiquitous computing: smart devices, environments and interaction 118

Multicasts: Transmissions for Multiple Receivers • Sending the same message from a single source to a defined group of multiple receivers, multicast communication or group communication is useful. Why? – • Hardware vs. software support Ubiquitous computing: smart devices, environments and interaction 121

Multicasts: Transmissions for Multiple Receivers • To avoid the overhead in managing large groups, groups can be split into hierarchies – • Messages can be tagged with sequenced identifiers to indicate ordering. • Acknowledgements can be used to support more reliable group communications. Ubiquitous computing: smart devices, environments and interaction 122

Multicasts: Transmissions for Multiple Receivers • Group membership may or may not be visible to the members depending upon the design. – ? ? ? Ubiquitous computing: smart devices, environments and interaction 123

Ubiquitous versus Localised Access • Networks can be designed for local context-aware access: • Used to tailor services for local needs. Ubiquitous computing: smart devices, environments and interaction 125

Ubiquitous versus Localised Access • Services can be restricted to local access because? – • Local services can also be designed to have access control Ubiquitous computing: smart devices, environments and interaction 126

Global Use: Low-cost Access Networks for Rural Use • In theory, wireless networks could be ubiquitous but in practice they aren’t in many regions. • Currently, the total worldwide Internet usage penetration was only about 18% but only about 4% in Africa (2007). • but 29% of the global population use GSM type mobile phone technology (2007), more if other types of mobile phone are also included. • People in some rural areas may not be able to pay much • Hence low-cost networks and access terminals are needed. Ubiquitous computing: smart devices, environments and interaction 128

Low-cost Access Networks for Rural Use: Cor. DECT system • Based on the DECT standard which initially was designed for use with cordless telephones. • Uses MC-TDMA to performs both time and frequency division in order to accommodate multiple channels. • Typically operates over distances of up to 10 KM with data rates supporting data rates of 35 and 70 kbps. T • Conventional listen before you talk type MAC is problematic when used in low bandwidth transmission over several km Ubiquitous computing: smart devices, environments and interaction 131

Internetworking Heterogeneous Networks • Different types of physical or links of the network have different signal capacities and have different signal attenuation and hence different requirements for signal amplification and repeaters. • Each type of physical media network, – e. g. , Ethernet, Point to Point Protocol (PPP) defines its own protocols to partition, structure data into packets for transmission. Ubiquitous computing: smart devices, environments and interaction 136

Separating Management and Control from Usage • Are different options for designing application use versus control and management of networks • Architectural model can separate concerns about: – media access, – control of the communication – management of the communication. Ubiquitous computing: smart devices, environments and interaction 138

Separating Management and Control from Usage • In some systems, each major application uses its own dedicated network, • Hence management is application (network) specific. • As multimedia content applications are becoming integrated into single networks, …. . Ubiquitous computing: smart devices, environments and interaction 142

Service-Oriented Networks Focus was on network oriented models • To use a service, users must subscribe to a particular network and service configuration on the network, – e. g. , voice calls via a telecoms network and audio-video content via an audio-video wireless broadcast network. Focus has now shifted to service- oriented models • Focus is on core networks that support multiple services • Services are coupled less to specific networks • Services can be available across heterogeneous networks Ubiquitous computing: smart devices, environments and interaction 145

Service-Orientation: in Edge Network Important design decision is whether or not to put the complexity or intelligence for service specific communication: • into the core network, – e. g. , PSTN • Or in the edge network • Or in both – e. g. , IP networks. Ubiquitous computing: smart devices, environments and interaction 148

Service-Orientation: in Edge Network • Motivation for end-to-end or edge-based complexity? • A main argument is that “functions placed at low levels of system may be redundant or of little value when compared with cost of providing them at that low level. ” • This implies that networks that are simple and neutral as possible should be used Ubiquitous computing: smart devices, environments and interaction 149

Service-Orientation: in Edge Network • Widespread adoption of IP in the core network has given the Internet a nearly universal interoperability – allows all end users to access Internet applications and content on a non discriminatory basis. • IP provide a network neutrality vision for comms & content delivery worlds in which every end user can obtain access to every available application and piece of information is quite compelling. • However, it has led to some content providers resisting more open access to the edge network as they will lose market share. Ubiquitous computing: smart devices, environments and interaction 150

Content-based Networks (CN) • CN is a network in which the flow of messages through the network is driven by the content of the messages, rather than by linking specific senders to specific receivers. • With this communication pattern, receivers subscribe to the types of content that are of interest to them without regard to any specific source (unless that is one of the selection criteria). • Senders simply publish information without addressing it to any specific destination. Ubiquitous computing: smart devices, environments and interaction 153

Programmable Networks • Typically, service providers do not have access to the router, in order to optimise network use for different applications. – e. g. , router control environments algorithms & router states, • This makes the deployment of new network services, which could be far more flexible than proprietary control systems, impossible due to the closed nature of network nodes. Ubiquitous computing: smart devices, environments and interaction 154

Overlay Network • An overlay network is a virtual network built on top of a physical network that provides a (virtual) infrastructure to one or more applications. • It handles the forwarding and handling of application data in ways that can differ from or in competition with the basic underlying physical network such as the Internet or PSTN. • It can be operated in an organised and coherent way by third parties, which may include collections of end-users. Ubiquitous computing: smart devices, environments and interaction 157

Overlay Network • Another issue is that different applications may need different levels of reliability, performance and latency and security and access control. – • Application specific overlay networks can be incrementally deployed on end-hosts running an overlay protocol, – Ubiquitous computing: smart devices, environments and interaction 159

Mesh Networks • In a full mesh network topology, every network node is connected using point-to-point connections to every other one. Cons? – connecting every node to every other node is costly to wire and costly power wise to transmit to each other. • Hence, in practice, mesh networks are usually partial mesh networks, in which each node is not connected to every other node. • Partial mesh networks tend to combine ring and star based network topologies. Ubiquitous computing: smart devices, environments and interaction 160

Wireless Mesh Networks (WMNs) • Are partial mesh, ad hoc, networks that can significantly improve the performance, at a lower cost and at a lower power output compared to other types of WLAN – • WMN is lower power because it uses a set of lower power multi-hop transmissions rather than needing a single more powerful transmission to base-station. • WNM may be a suitable solution in rural areas where conventional base-station wireless type network support or DSL support maybe patchy. • However, each WMN receiver is now more complex and more costly as it must also act as a relay. Ubiquitous computing: smart devices, environments and interaction 163

Wireless Mesh Networks (WMNs) • Instead of using a sophisticated and costly, centralised base stations, each wireless receiver in a WMN can act as a relay point or node for other receivers within range • -> WMN acts as a kind of cooperative network for its users. • WMNs can be used to ? ? –. Ubiquitous computing: smart devices, environments and interaction 164

Wireless Mesh Networks (WMNs) • In WMNs, each node operates not only as a host but also as a router (mesh–clients), forwarding packets on behalf of other nodes that may not be within direct wireless transmission range of their destinations • In addition, dedicated mesh routers which contain additional routing capabilities and bridging and gateway function to other networks. • WMN can also dynamically self-organise and self-configure mesh connectivity to support ad hoc multi-hop networking. Ubiquitous computing: smart devices, environments and interaction 165

Cooperative Networks • Some network access devices cannot access multiple networks in order to communicate, they just have access to 1 network connection • Some other network access devices have inbuilt support to heterogeneous network access, – e. g • Each of these networks must be used in isolation they do not interoperate. Ubiquitous computing: smart devices, environments and interaction 167

Cooperative Networks • Multiple types of the same type of physical and network layer may exist – because multiple independent users and providers may offer overlapping wireless networks within the same vicinity but yet again these do not interoperate. • These overlap and the coincidence of multiple overlapping networks will increase as more networks get installed but yet again these networks do no interoperate. Ubiquitous computing: smart devices, environments and interaction 168

Cooperative Networks • Cooperative communication is designed to enable singleantenna mobile access devices to reap some of the benefits of being Multiple Input Multiple Outputs (MIMO) systems • A specific problem that cooperative communication can solve at the physical media layer concerns signal fading – because thermal noise, shadowing due to fixed obstacles and due to signal attenuation can vary significantly over the course of a given transmission. • Transmitting independent copies of the signal that will face independent fading generates diversity and can effectively combat the deleterious effects of fading through combining these multiple signals. Ubiquitous computing: smart devices, environments and interaction 169